Quantitative magnetic resonance imaging of meniscal pathology ex vivo

Objective To determine the ability of conventional spin echo (SE) T2 and ultrashort echo time (UTE) T2* relaxation times to characterize pathology in cadaveric meniscus samples. Materials and methods From 10 human donors, 54 triangular (radially cut) meniscus samples were harvested. Meniscal pathology was classified as normal (n = 17), intrasubstance degenerated (n = 33), or torn (n = 4) using a modified arthroscopic grading system. Using a 3-T MR system, SE T2 and UTE T2* values of the menisci were determined, followed by histopathology. Effect of meniscal pathology on relaxation times and histology scores were determined, along with correlation between relaxation times and histology scores. Results Mean +/- standard deviation UTE T2* values for normal, degenerated, and torn menisci were 3.6 +/- 1.3 ms, 7.4 +/- 2.5 ms, and 9.8 +/- 5.7 ms, respectively, being significantly higher in degenerated (p < 0.0001) and torn (p = 0.0002) menisci compared to that in normal. In contrast, the respective mean SE T2 values were 27.7 +/- 9.5 ms, 25.9 +/- 7.0 ms, and 35.7 +/- 10.4 ms, without significant differences between groups (all p > 0.14). In terms of histology, we found significant group-wise differences (each p < 0.05) in fiber organization and inner-tip surface integrity sub-scores, as well as the total score. Finally, we found a significant weak correlation between UTE T2* and histology total score (p = 0.007, R-s(2) = 0.19), unlike the correlation between SE T2 and histology (p = 0.09, R-s(2) = 0.05). Conclusion UTE T2* values were found to distinguish normal from both degenerated and torn menisci and correlated significantly with histopathology.